1. Field of the Invention
The present invention relates generally to finishing machines and, more particularly, to an improved discharge door structure for vibratory finishing machines.
2. Prior Art
Vibratory finishing machines adapted to smooth and finish the surfaces of workpieces by such operations as deburring, burnishing, descaling and cleaning are well known. Such machines commonly employ a movably mounted processing tub for receiving a quantity of workpieces and abrasive finishing media. A finishing action is imparted to the workpieces by vibrating the tub.
As is brought out in the referenced patents, finishing media can conveniently be separated from workpieces after the media and workpieces are discharged from the tub. After separation, the finishing media may then be returned to the tub of the finishing machine for reuse. The finished workpieces may be conveyed to a separate unit or to a group of units for washing, drying, inspecting and packaging.
One basic type of vibratory finishing machine employs a horizontally disposed receptacle which is vibrated by eccentrics rotated about axes substantially paralleling the length of the receptacle. This first type of machine is known in the art as a "tub-type machine," and its receptacle is commonly called a "tub." A second type of machine employs an annular receptacle disposed in a substantially horizontal plane, and one or more eccentrics which vibrate the receptacle about a vertical axis located substantially centrally of the receptacle. This latter type of machine is known in the art as a "bowl-type machine," and its receptacle is often referred to as a "bowl". While the present invention is particularly well suited for use with tub-type machines, it may also be utilized with other types of finishing machines. Accordingly, it will be understood that neither the example given later in this patent of the practice of the invention in conjunction with a tub-type machine, nor use of the term "tub" in describing a machine receptacle is intended to limit the scope of the invention to use on tub-type machines.
Tub-type machines are often categorized as being either of the batch-type or of the continuous-feed-type. Some tub-type machines can be operated selectively in either batch-type or continuous-feed-type modes. In batch-type operation, the machine is loaded, a finishing operation is carried out, and the machine is them emptied. In continuous feed operation, media and workpieces are introduced into the tub near one end are finished as they precess in a churning-type movement along the length of the tub, whereupon they discharge together with the finishing media through a discharge opening at the opposite end of the tub. The present invention is operative with either batch-type or continuous-feed-type machines, or with finishing machines operated in either batch-type or continuous-feed-type modes.
The referenced Continuous Feed Patent, Object Sensor Patent, and Door Assembly Patent describes tub-type machines which are provided with discharge systems for controlling the rate at which a mixture of workpieces and finishing media discharges during a continuous-feed operation; while these machines may be operated on a batch-type basis if desired, they are designed primarily for continuous-feed operation wherein their discharge closures are opened and closed periodically to provide a controlled discharge of workpieces and media. The cycle of closure operation establishes an effective rate at which workpieces and media discharge from the tub which, in turn, determines the time span during which workpieces are retained in the finishing tub.
While the several referenced patents describe various types of closure systems for selectively opening and closing a discharge opening, a common drawback of each of these arrangements is that its discharge closure and operating mechanism are mounted on the machine's tub for movement therewith as the tub is vibrated. Since the discharge door and its operating mechanism are vibrated with the tub, these components must be built to withstand continuous vibration extending over a period of many years. This necessitates that the components be formed from relatively heavy materials which are precisely machined and sturdily bearinged to assure operational longevity.
A further drawback of mounting a discharge door and its operating mechanism on a vibratory finishing machine tub is that these components add weight to the tub and therefore require that the eccentrics which are vibrating the tub impart a greater amount of energy to the tub to effect its vibration. Moreover, where a door and its operating mechanism are mounted on a tub, these relatively heavy components may make it more difficult to vibrate the tub in a balanced, uniform fashion.
Still another problem with some previously proposed discharge closure systems is that, in order to effect mounting of the discharge closure and its operating mechanism on the tub, and in order to minimize the weight of these components, the discharge opening is often caused to be restricted in size beyond that which is desired. A further problem arising where efforts are made to minimize the weight of a discharge door and its operating mechanism is that the length of the path along which the door travels during opening and closing is kept as short as possible, whereby the door, when fully open, may still be found to at least slightly interfere with discharge of workpieces and finishing media from the tub. In short, design constraints imposed by the mounting of a discharge door and its operating mechanism on a vibratory finishing machine tub have, in some instances, prevented the type of full and free discharge of contents from the tub that is often desired.